In recent years, progress has been made in development of a valve opening characteristic control device making the valve opening characteristics, including the operating angle and/or amount of lift, of intake valves provided in a plurality of cylinders variable so as to control the amount of intake of an internal combustion engine. For example, the internal combustion engine disclosed in Japanese Unexamined Patent Publication (Kokai) No. 2002-155779 sets the operating angle and/or amount of lift relatively small so as to reduce pump loss from that of a conventional internal combustion engine and, at the same time, improve the mileage.
Both in the above-mentioned internal combustion engine provided with a valve opening characteristic control device for changing the valve opening characteristics and in an internal combustion engine of the prior art, sometimes the operating angle and/or amount of lift among cylinders deviates due to poor tuning or sometimes different amounts of deposits stick to the valves of the cylinders etc. Here, if setting the operating angle and/or amount of lift relatively small by a valve opening characteristic control device in an internal combustion engine provided with a valve opening characteristic control device, the amount of change to the intake air amount due to the poor tuning etc. becomes too great to ignored and consequently sometimes exerts an adverse influence upon the drivability and emission. Accordingly, it is necessary to correctly detect the variation of the valve opening characteristics, including the operating angle and/or amount of lift, among cylinders.
On the other hand, deviation of indicators of the state of combustion among cylinders also includes variation of the fuel injection amount. For this reason, if not considering the inter-cylinder variation of the fuel injection amount, the variation of the valve opening characteristics, including the operating angle and/or amount of lift, cannot be correctly detected. Accordingly, if variation of the fuel injection amount arises among cylinders, it is necessary to detect the variation of the valve opening characteristics after correctly detecting this variation of the fuel injection amount.
The present invention was made in consideration with such a circumstance and has as an object thereof to provide an inter-cylinder variation detection device and an inter-bank variation detection device of an internal combustion engine able to detect the occurrence of variation of the valve opening characteristics and the variation of the fuel injection amount among cylinders.